What Do The "+" and "-" Signs Indicate?

"+" denotes the notes of the octave higher than the octave you are playing in. 
"-" denotes one octave lower note.
e.g. If you are playing in the middle octave then:
C : middle octave C note
C+: Note C from one octave higher than middle
C- : Note C from one octave lower than middle

Western Notations Chart-

Western To Sargam-

C="Sa"    D="Re"                    C#="Ra (K)
E="Ga"    F="Ma"                    D#="Ga (K)
G="Pa"    A="Dha"                  F#="Ma (K)
B="Ni"     C="Sa"                    Ab="Dha (K)"
                                               Bb="Ni (K)